arXiv subjects

Jundan Nie

Publications and source records attributed to Jundan Nie.

At least 91 records · Page 5Linked to original sources

arXiv2020

The Third Data Release of the Beijing-Arizona Sky Survey

The Beijing-Arizona Sky Survey (BASS) is a wide and deep imaging survey to cover a 5400 deg$^2$ area in the Northern Galactic Cap with the 2.3m Bok telescope using two filters ($g$ and $r$ bands). The Mosaic $z$-band Legacy Survey (MzLS) covers the same area in $z$ band with the 4m Mayall telescope. These two surveys will be used for spectroscopic targeting of the Dark Energy Spectroscopic Instrument (DESI). The BASS survey observations were completed in 2019 March. This paper describes the third data release (DR3) of BASS, which contains the photometric data from all BASS and MzLS observations between 2015 January and 2019 March. The median astrometric precision relative to {\it Gaia} positions is about 17 mas and the median photometric offset relative to the PanSTARRS1 photometry is within 5 mmag. The median $5σ$ AB magnitude depths for point sources are 24.2, 23.6, and 23.0 mag for $g$, $r$, and $z$ bands, respectively. The photometric depth within the survey area is highly homogeneous, with the difference between the 20\% and 80\% depth less than 0.3 mag. The DR3 data, including raw data, calibrated single-epoch images, single-epoch photometric catalogs, stacked images, and co-added photometric catalogs, are publicly accessible at \url{http://batc.bao.ac.cn/BASS/doku.php?id=datarelease:home}.

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arXiv2019

The Sloan Digital Sky Survey Reverberation Mapping Project: Improving Lag Detection with an Extended Multi-Year Baseline

We investigate the effects of extended multi-year light curves (9-year photometry and 5-year spectroscopy) on the detection of time lags between the continuum variability and broad-line response of quasars at z>~1.5, and compare with the results using 4-year photometry+spectroscopy presented in a companion paper. We demonstrate the benefits of the extended light curves in three cases: (1) lags that are too long to be detected by the shorter-duration data but can be detected with the extended data; (2) lags that are recovered by the extended light curves but missed in the shorter-duration data due to insufficient light curve quality; and (3) lags for different broad line species in the same object. These examples demonstrate the importance of long-term monitoring for reverberation mapping to detect lags for luminous quasars at high-redshift, and the expected performance of the final dataset from the Sloan Digital Sky Survey Reverberation Mapping project that will have 11-year photometric and 7-year spectroscopic baselines.

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arXiv2019

The Sloan Digital Sky Survey Reverberation Mapping Project: Initial CIV Lag Results from Four Years of Data

We present reverberation-mapping lags and black-hole mass measurements using the CIV 1549 broad emission line from a sample of 349 quasars monitored as a part of the Sloan Digital Sky Survey Reverberation Mapping Project. Our data span four years of spectroscopic and photometric monitoring for a total baseline of 1300 days. We report significant time delays between the continuum and the CIV 1549 emission line in 52 quasars, with an estimated false-positive detection rate of 10%. Our analysis of marginal lag measurements indicates that there are on the order of 100 additional lags that should be recoverable by adding more years of data from the program. We use our measurements to calculate black-hole masses and fit an updated CIV radius-luminosity relationship. Our results significantly increase the sample of quasars with CIV RM results, with the quasars spanning two orders of magnitude in luminosity toward the high-luminosity end of the CIV radius-luminosity relation. In addition, these quasars are located at among the highest redshifts (z~1.4-2.8) of quasars with black hole masses measured with reverberation mapping. This work constitutes the first large sample of CIV reverberation-mapping measurements in more than a dozen quasars, demonstrating the utility of multi-object reverberation mapping campaigns.

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arXiv2019

Frequent flare events on the short-period M-type eclipsing binary BX Tri

We present long-term, multi-color photometric monitoring and spectroscopic observations of the short-period M-type eclipsing binary BX Tri. Six flare events were recorded in 4 years from 2014 to 2017. Three of them were detected on one night within an orbital cycle. The strongest one was identified on December 23, 2014. With the amplitudes of $Δ$B=0.48 mag, $Δ$V=0.28 mag, $Δ$R=0.10 mag, $Δ$I=0.02 mag, the total energy due to the flare event was measured to be 4.08 ($\pm$0.24) $\times$$10^{34}$ erg, exceeding the superflare level ($10^{34}$). Based on the observations, the evolutionary status of the binary system as well as the long-term orbital period changes were analyzed. It reveals that BX Tri is probably a semi-detached system with the primary component filling its Roche lobe. The extremely high occurrence of flare events of the binary could be related to the rapid mass transfer between components.

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arXiv2019

Observations of A Fast-Expanding and UV-Bright Type Ia Supernova SN 2013gs

In this paper, we present extensive optical and ultraviolet (UV) observations of the type Ia supernova (SN Ia) 2013gs discovered during the Tsinghua-NAOC Transient Survey. The photometric observations in the optical show that the light curves of SN 2013gs is similar to that of normal SNe Ia, with an absolute peak magnitude of $M_{B}$ = $-$19.25 $\pm$ 0.15 mag and a post-maximum decline rate $Δ$m$_{15}$(B) = 1.00 $ \pm $ 0.05 mag. \emph{Gehrels Swift} UVOT observations indicate that SN 2013gs shows unusually strong UV emission (especially in the $uvw1$ band) at around the maximum light (M$_{uvw1}$ $\sim$ $-$18.9 mag). The SN is characterized by relatively weak Fe~{\sc ii} {\sc iii} absorptions at $\sim$ 5000Å in the early spectra and a larger expansion velocity ($v_{Si}$ $\sim$ 13,000 km s$^{-1}$ around the maximum light) than the normal-velocity SNe Ia. We discuss the relation between the $uvw1-v$ color and some observables, including Si~{\sc ii} velocity, line strength of Si~{\sc ii} $λ$6355, Fe~{\sc ii}/{\sc iii} lines and $Δm_{15}$(B). Compared to other fast-expanding SNe Ia, SN 2013gs exhibits Si and Fe absorption lines with similar strength and bluer $uvw1-v$ color. We briefly discussed the origin of the observed UV dispersion of SNe Ia.

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arXiv2018

The First Data Release of the Beijing-Arizona Sky Survey

The Beijing-Arizona Sky Survey (BASS) is a new wide-field legacy imaging survey in the northern Galactic cap using the 2.3m Bok telescope. The survey will cover about 5400 deg$^2$ in the $g$ and $r$ bands, and the expected 5$σ$ depths (corrected for the Galactic extinction) in the two bands are 24.0 and 23.4 mag, respectively. BASS started observations in January 2015, and has completed about 41% of the whole area as of July 2016. The first data release contains both calibrated images and photometric catalogs obtained in 2015 and 2016. The depths of single-epoch images in the two bands are 23.4 and 22.9 mag, and the full depths of three epochs are about 24.1 and 23.5 mag, respectively.

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arXiv2018

The Second Data Release of the Beijing-Arizona Sky Survey

This paper presents the second data release (DR2) of the Beijing-Arizona Sky Survey (BASS). BASS is an imaging survey of about 5400 deg$^2$ in $g$ and $r$ bands using the 2.3 m Bok telescope. DR2 includes the observations as of July 2017 obtained by BASS and Mayall $z$-band Legacy Survey (MzLS). This is our first time to include the MzLS data covering the same area as BASS. BASS and MzLS have respectively completed about 72% and 76% of their observations. The two surveys will be served for the spectroscopic targeting of the upcoming Dark Energy Spectroscopic Instrument. Both BASS and MzLS data are reduced by the same pipeline. We have updated the basic data reduction and photometric methods in DR2. In particular, source detections are performed on stacked images, and photometric measurements are co-added from single-epoch images based on these sources. The median 5$σ$ depths with corrections of the Galactic extinction are 24.05, 23.61, and 23.10 mag for $g$, $r$, and $z$ bands, respectively. The DR2 data products include stacked images, co-added catalogs, and single-epoch images and catalogs. The BASS website (http://batc.bao.ac.cn/BASS/) provides detailed information and links to download the data.

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arXiv2018

Photometric calibration for the Beijing-Arizona Sky Survey and Mayall z-band Legacy Survey

We present the photometric calibration of the Beijing-Arizona Sky Survey (BASS) and Mayall z-band Legacy Survey (MzLS), which are two of the three wide-field optical legacy imaging surveys to provide the baseline targeting data for the Dark Energy Spectroscopic Instrument (DESI) project. The method of our photometric calibration is subdivided into the external and internal processes. The former utilizes the point-source objects of Pan-STARRS1 survey (PS1) as the reference standards to achieve the zero points of the absolute flux for individual exposures. And then the latter revise the zero points to make them consistent across the survey based on multiple tilings and large offset overlaps. Our process achieves a homogeneous photometric calibration over most of the sky with precision better than 10 mmag for g and r bands, 15 mmag for z band. The accuracy of the calibration is better than 1% at the bright end (16-18 mag) over most of the survey area.

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arXiv2017

Mapping the Tidal Disruption of the Hercules Dwarf: A Wide-Field DECam Imaging Search for RR Lyrae Stars

We investigate the hypothesized tidal disruption of the Hercules ultra-faint dwarf galaxy (UFD). Previous tidal disruption studies of the Hercules UFD have been hindered by the high degree of foreground contamination in the direction of the dwarf. We bypass this issue by using RR Lyrae stars, which are standard candles with a very low field-volume density at the distance of Hercules. We use wide-field imaging from the Dark Energy Camera on CTIO to identify candidate RR Lyrae stars, supplemented with observations taken in coordination with the Beijing-Arizona Sky Survey on the Bok Telescope. Combining color, magnitude, and light-curve information, we identify three new RR Lyrae stars associated with Hercules. All three of these new RR Lyrae stars lie outside its published tidal radius. When considered with the nine RR Lyrae stars already known within the tidal radius, these results suggest that a substantial fraction of Hercules' stellar content has been stripped. With this degree of tidal disruption, Hercules is an interesting case between a visibly disrupted dwarf (such as the Sagittarius dwarf spheroidal galaxy) and one in dynamic equilibrium. The degree of disruption also shows that we must be more careful with the ways we determine object membership when estimating dwarf masses in the future. One of the three discovered RR Lyrae stars sits along the minor axis of Hercules, but over two tidal radii away. This type of debris is consistent with recent models that suggest Hercules' orbit is aligned with its minor axis.

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arXiv2017

Ages and structural and dynamical parameters of two globular clusters in the M81 group

GC-1 and GC-2 are two globular clusters (GCs) in the remote halo of M81 and M82 in the M81 group discovered by Jang et al. using the {\it Hubble Space Telescope} ({\it HST}) images. These two GCs were observed as part of the Beijing--Arizona--Taiwan--Connecticut (BATC) Multicolor Sky Survey, using 14 intermediate-band filters covering a wavelength range of 4000--10000 Å. We accurately determine these two clusters' ages and masses by comparing their spectral energy distributions (from 2267 to 20000~Å, comprising photometric data in the near-ultraviolet of the {\it Galaxy Evolution Explorer}, 14 BATC intermediate-band, and Two Micron All Sky Survey near-infrared $JHK_{\rm s}$ filters) with theoretical stellar population-synthesis models, resulting in ages of $15.50\pm3.20$ for GC-1 and $15.10\pm2.70$ Gyr for GC-2. The masses of GC-1 and GC-2 obtained here are $1.77-2.04\times 10^6$ and $5.20-7.11\times 10^6 \rm~M_\odot$, respectively. In addition, the deep observations with the Advanced Camera for Surveys and Wide Field Camera 3 on the {\it HST} are used to provide the surface brightness profiles of GC-1 and GC-2. The structural and dynamical parameters are derived from fitting the profiles to three different models; in particular, the internal velocity dispersions of GC-1 and GC-2 are derived, which can be compared with ones obtained based on spectral observations in the future. For the first time, in this paper, the $r_h$ versus $M_V$ diagram shows that GC-2 is an ultra-compact dwarf in the M81 group.

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arXiv2017

Project Overview of the Beijing-Arizona Sky Survey

The Beijing-Arizona Sky Survey (BASS) is a wide-field two-band photometric survey of the Northern Galactic Cap using the 90Prime imager on the 2.3 m Bok telescope at Kitt Peak. It is a four-year collaboration between the National Astronomical Observatory of China and Steward Observatory, the University of Arizona, serving as one of the three imaging surveys to provide photometric input catalogs for target selection of the Dark Energy Spectroscopic Instrument (DESI) project. BASS will take up to 240 dark/grey nights to cover an area of about 5400 deg$^2$ in the $g$ and $r$ bands. The 5$σ$ limiting AB magnitudes for point sources in the two bands, corrected for the Galactic extinction, are 24.0 and 23.4 mag, respectively. BASS, together with other DESI imaging surveys, will provide unique science opportunities that cover a wide range of topics in both Galactic and extragalactic astronomy.

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arXiv2017

The Galactic extinction and reddening from the South Galactic Cap U-band Sky Survey: u band galaxy number counts and $u-r$ color distribution

We study the integral Galactic extinction and reddening based on the galaxy catalog of the South Galactic Cap U-band Sky Survey (SCUSS), where $u$ band galaxy number counts and $u-r$ color distribution are used to derive the Galactic extinction and reddening respectively. We compare these independent statistical measurements with the reddening map of \citet{Schlegel1998}(SFD) and find that both the extinction and reddening from the number counts and color distribution are in good agreement with the SFD results at low extinction regions ($E(B-V)^{SFD}<0.12$ mag). However, for high extinction regions ($E(B-V)^{SFD}>0.12$ mag), the SFD map overestimates the Galactic reddening systematically, which can be approximated by a linear relation $ΔE(B-V)= 0.43[E(B-V)^{SFD}-0.12$]. By combing the results of galaxy number counts and color distribution together, we find that the shape of the Galactic extinction curve is in good agreement with the standard $R_V=3.1$ extinction law of \cite{ODonnell1994}.

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arXiv2016

South Galactic Cap u-band Sky Survey (SCUSS): Data Release

The SCUSS is a deep $u$-band imaging survey in the south Galactic cap using the 2.3m Bok telescope. The survey observations were completed in the end of 2013, covering an area of about 5000 square degrees. We release the data in the region with an area of about 4000 deg$^2$ that is mostly covered by the Sloan digital sky survey. The data products contain calibrated single-epoch images, stacked images, photometric catalogs, and a catalog of star proper motions derived by Peng et al, 2015. The median seeing and magnitude limit ($5σ$) are about 2".0 and 23.2 mag, respectively. There are about 8 million objects having measurements of absolute proper motions. All the data and related documentations can be accessed through the SCUSS data release website of \url{http://batc.bao.ac.cn/Uband/data.html}.

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arXiv2015

South Galactic Cap u-band Sky Survey (SCUSS): Data Reduction

The South Galactic Cap u-band Sky Survey (SCUSS) is a deep u-band imaging survey in the Southern Galactic Cap, using the 90Prime wide-field imager on the 2.3m Bok telescope at Kitt Peak. The survey observations started in 2010 and ended in 2013. The final survey area is about 5000 deg2 with a median 5-sigma point source limiting magnitude of about 23.2. This paper describes the survey data reduction process, which includes basic imaging processing, astrometric and photometric calibrations, image stacking, and photometric measurements. Survey photometry is performed on objects detected both on SCUSS u-band images and in the SDSS database. Automatic, aperture, point-spread function (PSF), and model magnitudes are measured on stacked images. Co-added aperture, PSF, and model magnitudes are derived from measurements on single-epoch images. We also present comparisons of the SCUSS photometric catalog with those of the SDSS and CFHTLS.

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arXiv2015

Photometric Metallicity Calibration with SDSS and SCUSS and its Application to distant stars in the South Galactic Cap

Based on SDSS g, r and SCUSS (South Galactic Cap of u-band Sky Survey) $u$ photometry, we develop a photometric calibration for estimating the stellar metallicity from $u-g$ and $g-r$ colors by using the SDSS spectra of 32,542 F- and G-type main sequence stars, which cover almost $3700$ deg$^{2}$ in the south Galactic cap. The rms scatter of the photometric metallicity residuals relative to spectrum-based metallicity is $0.14$ dex when $g-r<0.4$, and $0.16$ dex when $g-r>0.4$. Due to the deeper and more accurate magnitude of SCUSS $u$ band, the estimate can be used up to the faint magnitude of $g=21$. This application range of photometric metallicity calibration is wide enough so that it can be used to study metallicity distribution of distant stars. In this study, we select the Sagittarius (Sgr) stream and its neighboring field halo stars in south Galactic cap to study their metallicity distribution. We find that the Sgr stream at the cylindrical Galactocentric coordinate of $R\sim 19$ kpc, $\left| z\right| \sim 14$ kpc exhibits a relative rich metallicity distribution, and the neighboring field halo stars in our studied fields can be modeled by two-Gaussian model, with peaks respectively at [Fe/H]$=-1.9$ and [Fe/H]$=-1.5$.

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arXiv2015

An Investigation of the Absolute Proper Motions of the SCUSS Catalog

Absolute proper motions for $\sim$ 7.7 million objects were derived based on data from the South Galactic Cap u-band Sky Survey (SCUSS) and astrometric data derived from uncompressed Digitized Sky Surveys that the Space Telescope Science Institute (STScI) created from the Palomar and UK Schmidt survey plates. We put a great deal of effort into correcting the position-, magnitude-, and color-dependent systematic errors in the derived absolute proper motions. The spectroscopically confirmed quasars were used to test the internal systematic and random error of the proper motions. The systematic errors of the overall proper motions in the SCUSS catalog are estimated as -0.08 and -0.06 mas/yr for μα cos δ and μδ, respectively. The random errors of the proper motions in the SCUSS catalog are estimated independently as 4.2 and 4.4 mas/yr for μα cos δ and μδ. There are no obvious position-, magnitude-, and color-dependent systematic errors of the SCUSS proper motions. The random error of the proper motions goes up with the magnitude from about 3 mas/yr at u < 18.0 mag to about 7 mas/yr at u = 22.0 mag. The proper motions of stars in SCUSS catalog are compared with those in the SDSS catalog, and they are highly consistent.

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arXiv2015

Capability of Quasar Selection by Combining the SCUSS and SDSS Observations

The South Galactic Cap $u$-band Sky Survey (SCUSS) provides a deep $u$-band imaging of about 5000 deg$^2$ in south Galactic cap. It is about 1.5 mag deeper than the SDSS $u$-band. In this paper we evaluate the capability of quasar selection using both SCUSS and SDSS data, based on considerations of the deep SCUSS $u$-band imaging and two-epoch $u$-band variability. We find that the combination of the SCUSS $u$-band and the SDSS $griz$ band allows us to select more faint quasars and more quasars at redshift around 2.2 than the selection only with the SDSS $ugriz$ data. Quasars have significant $u$-band variabilities. The fraction of quasars with large two-epoch variability is much higher than that of stars. The selection by variability can select both low-redshift quasars with ultraviolet excess and mid-redshift ($2 < z <3.5$) quasars where quasar selection by optical colors is inefficient. The above two selections are complementary and make full use of the SCUSS u-band advantages.

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arXiv2014

The 0.1<z<1.65 evolution of the bright end of the [OII] luminosity function

We present the [OII] luminosity function measured in the redshift range 0.1<z<1.65 with unprecedented depth and accuracy. Our measurements are based on medium resolution flux-calibrated spectra of emission line galaxies with the FORS2 instrument at VLT and with the SDSS-III/BOSS spectrograph. The FORS2 spectra and the corresponding catalog containing redshifts and line fluxes are released along with this paper. In this work we use a novel method to combine the aforementioned surveys with GAMA, zCOSMOS and VVDS, which have different target selection, producing a consistent weighting scheme to derive the [OII] luminosity function. The measured luminosity function is in good agreement with previous independent estimates. The comparison with two state-of-the-art semi-analytical models is good, which is encouraging for the production of mock catalogs of [OII] flux limited surveys. We observe the bright end evolution over 8.5 Gyr: we measure the decrease of log L* from 42.4 erg/s at redshift 1.44 to 41.2 at redshift 0.165 and we find that the faint end slope flattens when redshift decreases. This measurement confirms the feasibility of the target selection of future baryonic acoustic oscillation surveys aiming at observing [OII] flux limited samples.

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